Method for drilling and coring

ABSTRACT

A method of drilling bore holes which enables a cylindrical solid core sample to be obtained from a formation. A coring bit together with a core barrel and concentrically arranged drill pipe provides central and annular passageways. The annular passageway is used for circulating fluid to the bit and back up the bore hole annulus while the central passageway provides for the return of drilling fluid and cores. The circulating fluid is forced down through the drill string annulus to the drill bit, and back up through the hole annulus to thereby remove debris and cool the bit in an improved manner. The cores which have been cut by the bit are accumulated within the core barrel and from time to time the pressure of the drilling fluid is increased while the central passageway is opened to the flow of fluid, thereby forcing the fluid to flow into and up through the central passageway, carrying the accumulated cores therewith. A predetermined pressure drop is maintained across the face of the diamond bit by adjusting the bearing pressure thereof with respect to the formation to thereby enable the bit to cooperate with the formation in a manner analogous to the action of a valve.

United States Patent Wayland D. Elenburg P. O. Box 1588, Monahans, Tex.79756 [21] Appl. No. 825,524 [22] Filed May 19, 1969 Division of Ser.No. 714,551, Mar. 20, 1968, Pat. No. 3,473,517. [45] Patented May 11,1971 [72] lnventor [54] METHOD FOR DRILLING AND CORING 3,338,322 8/1967Henderson Examiner-Emest R. Purser Assistant Examiner-Richard E. FavreauAttorney-Marcus L. Bates ABSTRACT: A method of drilling bore holes whichenables a cylindrical solid core sample to be obtained from a formation.A coring bit together with a core barrel and concentrically arrangeddrill pipe provides central and annular passageways. The annularpassageway is used for circulating fluid to the bit and back up the borehole annulus while the central passageway provides for the return ofdrilling fluid and cores. The circulating fluid is forced down throughthe drill string annulus to the drill bit, and back up through the holeannulus to thereby remove debris and cool the bit in an improved manner.The cores which have been cut by the bit are accumulated within the corebarrel and from time to time the pressure of the drilling fluid isincreased while the central 7 passageway is opened to the flow of fluid,thereby forcing the fluid to flow into and up through the centralpassageway, carrying the accumulated cores therewith. A predeterminedpressure drop is maintained across the face of the diamond bit byadjusting the bearing pressure thereof with respect to the formation tothereby enable the bit to cooperate with the forma tion in a manneranalogous to the action of a valve.

.PATENTED Mm 1 IHYI SHEEIIUFZ IN VENTOR. WAYLAND D. ELENBURG BY MARCUSL. BATES PATENTEU mm 1197.

SHEET 2 BF 2 R. U m8. m mL E D D N A w. A .l W 6. s a w: I w

MARCUS L. BATES METHOD FOR DRILLING AND CORING CROSS-REFERENCE TORELATED APPLICATIONS This application is a division of my copending Pat.application Ser. No. 7l4,55l, filed Mar. 20, 1968 now U.S. Pat. No.3,473,5l7 issued Oct. 21, 1969. BACKGROUND OF THE INVENTION In order toobtain geological samples of formations located in the earths structure,a diamond bit is often utilized which enables a cylindrical elongatedsample of the formation to be cut into predetermined lengths, calledcores." The core passes through the bit as the diamonds on the face ofthe bit cut away a portion of the formation while the borehole is beingdrilled. By using a diamond bit of this design, a more representativesample is obtained as compared to the chip drilling operation" whereinlarge cuttings or chips are relied upon for analysis. In using drillingand coring apparatus of this type, it has been found satisfactory tocarry out the coring operation until a core barrel is tilled with theindividual lengths of cores. During the coring operation, thecirculation pattern of the drilling fluid can be traced down through theannulus of the drill string and back up through the hole annulus wherethe fluid flows into a mud pit. When it is desired to retrieve thecores, the central tubing is opened causing the flow path to change. Thedrilling fluid continues to travel down through the annulus of the drillstring but now is caused to reverse its flow path where the major flowoccurs back up through the central tubing string, carrying the corestherewith to the surface of the earth. In the past art, the cuttings arecarried away by the drilling fluid which is directed through passagewayslocated in the drill bit and which communicate with the hole annulusrather than the central portion of the drill. Accordingly, when it isdesired to change the circulation pattern, the bit is usually raised orelevated slightly in order to allow the circulation flow path to occuracross the bit and back up through the central passageway, carrying thecores to the surface of the earth. This method of drilling requirestremendous pump pressure inasmuch as the fluid tends to flow along thepath of least resistance and is therefore divided into two flow paths,one of which follows the hole annulus, and the other being through thecore barrel and up the central tubing.

SUMMARY OF THE INVENTION The present invention comprehends both methodand apparatus for carrying out an improved boring and coring operationwhile forming a borehole. Concentrically arranged drill pipe having acentral and annular passageway formed therein for circulating fluid tothe bit and for providing a return flow path for obtaining the core issuitably connected to a bit by a combination sub and core barrel.Drilling fluid is forced down through the annulus of the drill pipe ordrill string and into close proximity of the diamond or otherwise facedcutting teeth of the bit, with a passageway being radially disposedabout the inside central portion of the bit, outwardly of the corereceiving annulus. This flow path causes the fluid to be forced withhigh velocity across the diamonds of the drill bit whereupon the flowthen circulates back to the surface of the earth through the holeannulus. Accordingly, the pressure drop across the bit can be controlledby the pressure of the diamonds as they are forced into cuttingrelationship with respect to the formation. Total flow across the entirebit face maintains the bit cool and clean of debris, and enables the bitto cooperate with the formation with a valvelike action. When it isdesired to circulate the accumulated cores out of the core barrel, thefluid pressure is increased a predetermined amount while the bit ismaintained in drilling relationship, or close contact with the fonnationto thereby force the major portion of the fluid flow back up the centraltubing and pushes the cores to the surface of the earth in-an improvedmanner. All this time the drilling operation continues since this methodprovides sufficient flow across the bit to protect the diamond face.

The apparatus used in carrying out the present invention includes thebefore-mentioned drill bit and drill string with the bit being connectedto the string by a sub. The sub supports a core barrelwherein the corebarrel is rotatably secured to the sub with the lower marginal end ofthe barrel being secured in a nonrotating manner to the core which isbeing cut to thereby prevent rotation of the barrel and accordingly,improving the quality of the core. A valve means located above theground and associated with the central tubing, along with the valvelikeaction of the bit enables the above method to be carried out. 4

It is therefore a primary object of the present invention to provide amethod of obtaining cores from a borehole by circulating the cores backto the surface of the earth by an improved flow pattern.

Another object of the present invention is the provision of a methodwhich enables coring operations to be carried out by an improvedcirculation pattern.

A further object of the present invention is the provision of a bithaving an improved flow path across a coring or cutting face thereof.

Another object of the present invention is the provision of an improvedcombination which includes a coring bit, sub, and core barrel and whichenables cores to be obtained in an improved manner.

The above objects are attained in accordance with the present inventionby the provision of concentrically arranged drill pipe which areconnected to a bit and to a nonrotating core barrel which all cooperatetogether to provide an improved flow path across a bit.

Other objects of the present invention will become apparent to thoseskilled in the art as the description proceeds. BRIEF DESCRIPTION OF THEDRAWINGS FIG. 1 is a diagrammatical representation of a cross section ofthe earths structure with the present well boring apparatus beingpositioned therein in order to explain the operation of the invention;

7 FIG. 2 is an enlarged cross-sectional view of part of the device seenin FIG. I;

FIG. 3 is a fragmentary cross-sectional view taken along line 3-3 ofFIG. 2; and

FIG. 4 is a fragmentary cross-sectional representation of the inventionwhich has been taken along line 4-4 of FIG. 2. DETAILED DESCRIPTION OFTHE INVENTION FIG. 1 schematically sets forth a portion of a welldrilling apparatus 10 which is in the act of boring a hole into theearths structure 11. Part of the apparatus is located above the surfaceof the earth as seen at 12 while the remainder of the apparatus islocated below the surface of the earth. A high pressure inlet 14provides a flow of drilling fluid to the uppermost part of a swivel orthe like, schematically illustrated by numeral I6, while fluid isreturned from the borehole either by means of a gooseneck l8 upwardlyalong the hole annulus 20, depending upon the circulation patterndesired.

A rotatable drill pipe 22 telescopingly receives a longitudinallyextending, centrally positioned tubing 24 therewithin, with the drillpipe and tubing being connected together from several joints in theusual manner to form a drill string, as is known to those skilled in theart. At the terminal end of the drill string there is located an outerbarrel or sub 25 which carries a diamond bit 26 threadedly attached tothe lower depending end thereof. As the bit is rotated by the drillstring, a core 28 is formed within the central aperture of the bit, withthe core extending upwardly where it is received within a core barrel30. The core is broken into uniform lengths such as indicated by thearrow at numeral 32., The core barrel is rotatably attached to the outerbarrel or sub by the illustrated journal means 34. The sub includesradially spaced-apart passageways extending therethrough for isolatingthe drilling fluid from the bearing, and to enable the fluid to flow tothe drill bit as well as to provide a means for the flow of theaccumulated cores back up through the central tubing from time to time.

The rotatable barrel includes spaced-apart guide means 33 formaintaining the lower terminal end of the barrel properly aligned withthe outer barrel, so as to assure cutting a uniform core. Numerals 36and 38 indicate spaced-apart hypothetical voids, sometime calledfractures" or fissures." The void 36 has been drilled through orpenetrated, and fluid can escape up hole annulus 40 into the void. Thebit has also penetrated to a position where it rests on the bottom ofthe void 38 and drilling fluid can escape thereinto also. The purpose ofillustrating the two spaced-apart voids will be realized later on.

Looking now to FIG. 2, wherein an enlarged cross-sectional view of thebefore-mentioned outer and inner barrel and bit are shown in detail. Itshould be understood that the device of FIG. 2 is connected to the drillstring and related apparatus of FIG. 1. The annulus formed between theinner and outer tubing provides an annular passageway 44 with the corebarrel being attached to the sub by means of a bearing such as seen at46. A collar 48 threadedly engages the core barrel in a manner tocapture the bearing therebetween as illustrated at 50. The centralportion 52 of the barrel extends downwardly to where it threadedlyengages member 54, the depending end of which forms a shoulder at 55. Acore breaker 58 commences near shoulder 55 and longitudinally extends inan upward and outward direction for a limited length with respect to theinside peripheral wall surface of the core barrel. The core breaker ispreferably circumferentially coextensive with the inside peripheral wallsurface for approximately thereof, and is several times longer in lengthas compared to its width. The vertical distance between the core breakerand the drill bit face determines the length of the individual cores.

Threadedly attached to the lower terminal end of the core breaker memberis a cylindrical downwardly converging core catcher housing 60 having akey 62 thereon, and which includes vertically spaced-apart splinesthereon (not shown) which cooperate with similar spaced-apart splinesprovided on the outside peripheral wall surface of the invertedfrustoconical core catcher 64, the details of which are best seen inFIG. 3. The lower tenninal end portion of the core barrel terminates at61. The inside face of the drill bit is provided with grooves 67, havinga bottom-most portion 68, to thereby leave a passageway between thelower terminal end of the inner barrel and the inside of the bit.

The face of the bit containing the diamonds is generally seen at 66,with the lower inside portion of the bit being provided with thebefore-mentioned grooves which permit the passage of fluid to beforcibly bent across the inside peripheral portion 69 which forms thecentral aperture of the bit. Accordingly, a passageway 70 is formedbetween the outer peripheral surface of the various members which formsthe core barrel and the inside peripheral wall surface of the outerbarrel. The passageway continues as seen at 73 to where it branches intoa multiplicity of radially spaced-apart passageways 74 which are drilledthrough the before-mentioned sub 42 so as to communicate at 75 with theannular passageway formed by the drill string.

Looking again now to FIG. 3, in conjunction with FIGS. 1 and 2, whereinthe before-mentioned core catcher is better il lustrated. As seenillustrated therein, as stated above, the core catcher includes amultiplicity of splines 80 which cooperate with similar but oppositelydisposed splines 82 formed on the inside peripheral wall surface of corecatcher housing 60. Edge portion 84 of the expandable core catchercooperates with the before-mentioned key 62 with the edge portion 84being slidably and guidably received by the key to thereby enablereciprocation of the core catcher between the limits provided byshoulder 55 and the illustrated position of the core catcher in FIG. 2.

As seen in FIG. 4, the lower guide means 33 are each preferably located90 apart and extend for a limited distance about the annulus 73 so as toleave passageway 72 therebetween. The core barrel rotates against theinside surface area forrned by the outwardly directed guide member.

Looking again to FIG. I, there is further seen illustrated an inletvalve .92 with leads to the high pressure source of drilling fluid.Outlet valve 94 controls the fluid flow' through gooseneck 18 to therebypermit the cores to be caught on a conventional mud screen 96 as thecores are circulated from the borehole.

In order to catch elongated sections of core which extend from more than5 inches in length, the core can alternatively be telescopingly receivedthrough the tubing 97, which includes a hinged flange .98 to permit thecore catching cylindrical portion 99 to be separated from lower portion97. Drain apertures 102 are provided in the tubing 97. It will berealized by those skilled in the art that the section 97, 98, 99,-and102 is best placed with its central axis in alignment with the centralaxis of the tubing 24, i.e., elements 97-l02 replace the gooseneck I8.

OPERATION In operation, with the apparatus of the present inventionassembled as schematically illustrated in FIG. I, the diamond bitcontinuously cuts a core. As the core enters the central aperture formedby inside peripheral portion 69 of the bit, the core forces its wayupwardly through the core catcher. Since the core catcher has splineswhich cooperate with the splined inner surface of the core catcherhousing, the core barrel remains affixed to the telescopingly receivedcore as the outer barrel rotates about the journal formed by bearing 46.

As the coremoves into the barrel, it contacts the core breaker whichplaces a sheer or transverse force on the core body, whereupon the corebreaks into uniform lengths with each length of core being accumulatedwithin the core barrel. Since the core breaker and barrel are stationarywith respect to the core, the core sample is received in uniformundamaged cylindrical pieces.

During this stage of the operation, drilling fluid enters through inlet14 where it travels down the annulus of the drill string and at thefluid is diverted into a multiplicity of radially spaced-apartpassageways 74, where the fluid then travels down through passageway 73and between the four spacedapart guide means, to where the fluid can nowenter annulus 70. From annulus 70 the fluid travels through thepassageways formed between the lower depending end 61 of the core barreland through the multiple grooves 67 formed on the inside lower wallportion of the bit. Since valve 94 of the gooseneck is closed, the fluidmust now flow across the diamonds located in the cutting face of thedrill bit and back up the hole annulus, carrying the cuttings from theformation with it during its upward travel back to the surface of theearth. The rate of drilling during this time is preferably controlled byobserving the pressure drop across the face of the bit rather than byutilizing a weight indicator in the conventional manner. A pressure dropof pounds across the face of the drill bit is desirable for mostapplications, although this figure will usually be changed whenencountering unusual formations.

For example, a 2 /e-inch core, received withing a ZA-inch tube, using a4/s-inch bit attached to a 4k-inch outside diameter drill pipe providedexcellent core samples and exceptionally long bit service when using adrilling fluid flow rate of 40 gallons per minute when coring, and 150gallons per minute when circulating the cores to the surface.

The pressure drop across the bit face was adjusted by lifting the bitface free of the formation floor, observing the hydrostatic head at 14,and cautiously setting the bit down until the indicated pressureincreased an additional 150 pounds per square inch, which is thepressure drop across the bit. This value provides a reasonable rate ofpenetration while maintaining the diamonds of the bit sufficientlycooled and cleaned to thereby prolong the bit life. It should beunderstood that the recited pressure drop of 150 pounds is measuredacross the cutting surface of the bit, and is exclusive of thehydrostatic head or the friction head of the drill pipe.

While the above operation is described as being carried out by using aliquid drilling mud," it is also contemplated to use air or othercompressible fluid, as well as a combination thereof.

the hole annulus, is restricted to thereby enable a substantial rise inpressure at the drill stem. The flow restriction is then removed fromthe central tubing by opening the valve associated therewith, whereuponthe pressure drop across the cores located in the core barrel forces thecores up through the central passageway of the drill string and throughthe gooseneck, much like the operation of a piston within a cylinder.

Often it is desirable to use a combination of air and liquid, especiallywhere a strong aquifier is encountered. In this instance, it ispreferable to circulate the cores to the surface by restricting the flowof fluid from the bore hole by utilizing the valve action between thedrill bit and the formation. Compressed gas is supplied to the drillstring annulus, and when the pressure reaches a suitable value, openingof the valve associated with the central tubing enables circulation ofthe cores to the surface.

Where air alone fails to properly circulate the cores to the surface, itis possible to admix water or mud with the air which is being used asthe return fluid, to thereby provide more body to the fluid in order tobetter circulate the cores from the core barrel to the gooseneck.

The improved circulation pattern includes forcibly flowing fluid throughpassageways 67 located on the lower inside face of the bit, wherein theflow is forced to proceed directly across the bit face to where thedrilling fluid then returns up the hole annulus. This improved flowpattern causes all of the drilling fluid to be forced across thedrilling face, and when encountering voids or fissures, such as seen at38, escape of drilling fluid into the formation does not result indestruction of the diamonds as usually occurs when using a conventionalcirculation system. Therefore, even under conditions wherein there is acomplete loss of circulation, the improved bit is safely provided withadequate fluid flow ther'eacross, so long as fluid enters at 92.

Accordingly, by forcibly pumping fluid from inside the bit to an areaexternally of the bit assures the cutting face of the bit of alwayshaving a cleaning and cooling fluid. This improved method enables thediamonds located in the cutting face of the bit to engage the formationat a smaller cutting depth, while still maintaining a satisfactory rateof penetration. Should the diamonds suddenly engage a harder or tougherformation,vthe individual diamonds will not be torn from the bit andlost.

As indicated by the arrow at numeral 90, the cutting face of the bitseats against the undrilled or remaining portion of the formation withan action similar to that of a valve; that is, when the bit bearsagainst the formation with a large force, the pressure drop across theface of the bit must be increased in order to maintain the same flowrate of drilling fluid, and with thebit slightly displaced from theformation, a larger flow of fluid is required in order to maintain thesame pressure drop. Therefore, the cooperation between the cutting faceof the bit and the formation which is to be removed can be controlled byobservation of the pressure drop as measured at 14.

As the core is cut, the fluid within the central tubing and core barrelis quiescent which eliminates the heretofore undesirable erosion orwashing of the accumulated samples.

As a core is being cut (as illustrated at 28 in FIG. 1), the corecatcher (seen at 64 in FIG. 2) travels upwardly within its housing as itexpands to accept the core therethrough. The

core catcher continues its upward travel until the upper edge portion ofthe core catcherabuts against face 55 of the barrel, thereby permittingthe core to slide through the catcher and into the barrel. This actionpermits the edge portions 84 of the core catcher to expand with the corebeing forced therebetween and up into the barrel where it bears againstthe inwardly sloped face of the core breaker 58. The core breakerimparts sufficient sheer or lateral force into the core to cause it tobreak into uniform lengths whereupon the cores may accumulate or stackup within the core barrel until it is desired to'circjulate them back tothe' surface of the earth in the before-described manner. 7

As further seen in FIG. 2, in conjunction with FIG. 1, the diamond bitis removably attached in a conventional manner to the outer tube 25which in turn is threadedly attached to the sub 42 with the subthreadedly attaching the entire combination to the drill string. Theentire device is easily broken down into its various components bymerely removing the outer tube 25 and the inner tube connector 45 so asto enable the bearing 46 to be pressed therefrom. The core breaker andthe lowermost member which contains the core catcher are threadedlydisengaged from the main body of the core barrel by the indicatedthreaded connections.

The down time required for the coring operation of the present inventionis negligible, which, coupled with the increased efficiency of operationbrought about by utilizing the present method enables a substantialincrease of footage drilled per unit of time.

While the core barrel of the present invention is of the nonrotatingtype, it is contemplated to use the present invention in conjunctionwith other types of core barrels.

While I have illustrated and described a preferred embodiment of myinvention it is to be understood that such is merely illustrative andnot restrictive'and that variations and modifications may be madetherein without departing from the spirit and scope of the invention. Itherefore do not wish to be limited to the precise details set forth butdesire to avail myself of such changes as fall within the purview of myinvention.

I claim:

1. A method of drilling boreholes and obtaining cores therefrom,wherein'a drill bit is connected to concentrically arranged drill pipewhichforms a central and annular passageway for circulating fluid to andfrom the bit, comprising the steps of:

l. circulating drilling fluid down through the drill string annulus,across the cutting face of the drill bit, and back up throughtheborehole annulus, while'the bit cuts cores to form the borehole;

2. accumulating the cut cores in a core barrel;

3. arranging the core barrel in joumaled relationship with respect tothe drill pipe and stationary with respect to the formation byinterlocking the core-which is being cut with structure associated withthe core barrel;

- 4. retrieving the cores'of step (2) by increasing the flow ofdrillingfluid while maintaining the bit in cutting relationship to theformation and circulating a major portion of the fluid from the drillstring annulus into the core barrel and back up the central passagewayto thereby provide an increased pressure drop across the cores in thecore barrel which causes the accumulated cores to move from the corebarrel to the surface of the earth.

2. A method of drilling boreholes and obtaining cores therefrom, whereina drill bit is connected to concentrically arranged drill pipe whichforms a central and annular passageway for circulating fluid to and fromthe bit, comprising the steps of:

l. circulating drilling fluid down through the drill string annulus,across the cutting face of the drill bit, and back up through theborehole annulus, while the bit cuts cores to form the borehole;

2. breaking the core into convenient lengths which will facilitate theirremoval from the borehole;

3. accumulating several lengths of cut core in a core barrel,

4. retrieving the cores of step (3) by increasing the flow of drillingfluid while maintaining the bit in cutting relationship to the formationto thereby provide an increased pressure drop across the cores in thecore barrel;

5. circulating a major portion of the fluid from the drill stringannulus, into the core barrel, and back up the central passageway whenit is desired to retrieve the accumulated cores from the core barrel tothe surface of the earth.

3. The method of claim 2 wherein the following additional step isincluded:

6. interlocking the core which is being cut with structureassociatedwith the core barrel to thereby enable the core barrel toremain stationary with respect to the formation and to rotate withrespect to the drill pipe.

4. The method of claim 2 wherein step (4) includes the followingadditional steps:

a. restricting the flow of fluid from the borehole annulus by using theaction of the drill bit against the formation as a valve means;

b. supplying a source of compressible fluid pressure to the annulus ofthe drill string;

c. releasing the flow restriction from the central passageway to therebypermit the flow of liquid, cores, and compressed fluid therethrough.

5. A method of drilling boreholes and obtaining cores therefrom, whereinthe drill bit is connected to concentrically arranged drill pipe whichforms a central and annular passageway for circulating fluid to and fromthe bit, comprising the steps of:

1. using liquid drilling mud as the drilling fluid to thereby cool thedrill bit while lubricating the hole annulus, and wherein the flow tothe bit is caused to flow across the bit face;

2. Controlling therate of penetration of the bit by maintaining aconstant pressure drop across the face of the bit to thereby prolong thelife of the bit;

3. circulating drilling fluid down through the drill string annulus,across the cutting face of the drill bit, and back up through theborehole annulus, while the bit cuts cores to form the borehole;

4. accumulating the cut cores in a core barrel;

5. retrieving the cores of step (4) by increasing the flow of drillingfluid while maintaining the bit in cutting relationship to the formationto thereby provide an increased pressure drop across the cores in thecore barrel; and, circulating a major portion of the fluid from thedrill string annulus, into the core barrel, and back up the centralpassageway to thereby cause the accumulated cores to move from the corebarrel to the surface of the earth.

6. The method of claim 5 wherein the following additional step isincluded:

6. interlocking the core which is being cut with structure associatedwith the core barrel to thereby enable the core barrel to remainstationary with respect to the formation and to rotate with respect tothe drill pipe.

7. The method of claim 5 wherein step (5) includes the followingadditional steps: I

a. restricting the flow of fluid from the borehole annulus by using theaction of the drill bit against the formation as a valve means;

b. supplying a source of compressible fluid pressure to the annulus ofthe drill string;

c. releasing the flow restriction from the central passageway to therebypermit the flow of liquid, cores, and compressed fluid tlterethrough.

8. A method of drilling boreholes and obtaining cores therefrom, whereina drill bit is connected to concentrically arranged drill pipe whichforms a central and annular passageway for circulating fluid to and fromthe bit, comprising the steps of:

l. circulating drilling fluid down through the drill string an nulus,across thecutting face of the drill bit, and back up through theborehole annulus, while the bit cuts cores to form the borehole;

2. accumulating the cut cores in a core barrel;

3. retrieving the cores of step (2) byv the following additional steps:

a. restricting the flow of fluid from the borehole and from the centralpassageway of the drillstring while increasing the pressure at the drillstring annulus to thereby cause a rise in pressure at the drill bit;

b. maintaining the bit in cutting relationshipto the formation;

c. removing the flow restriction from the central passageway andcirculating a major portion of the fluid from the drill string annulus,into the core barrel, and back up the central passageway to therebyprovide a pressure drop across the cores of step (2) in order to forcethe cores up through the central passageway of the drill string.

9. The method of claim 8 wherein the following additional step isincluded:

4. interlocking the core which is being cut with structure associatedwith the core barrel to thereby enable the core barrel to remainstationary with respect to the formation and to rotate with respect tothe drill pipe.

10. A method of drilling boreholes and obtaining cores therefrom,wherein the drill bit is connected to concentrically arranged drill pipewhich forms a central and annular passageway for circulating fluid toand from the bit, comprising the steps of:

l. circulating drilling fluid down through the drill string annulus,across the cutting face of the drill bit, and back up through theborehole annulus, while the bit cuts cores to form the borehole;

. accumulating the cut cores in a core barrel; restricting the flow offluid from the central passageway of the drill pipe while carrying outstep (2); 4. retrieving the cores of step (2) by carrying out thefollowing steps:

a. restricting the flow of fluid from the borehole annulus by using theaction of the drill bit against the formation as a valve means;

b. supplying a source of compressible fluid pressure to the annulus ofthe drill string;

0. increasing the flow pressure of the drilling fluid while maintainingthe bit in cutting relationship to the forma- HOD d. releasing the flowrestriction from the central passageway to thereby permit a majorportion of the fluid to flow from the drill string annulus, into thecore barrel, and back up the central passageway so as to move theaccumulated cores from the core barrel to the surface of the earth.

I]. The method of claim 10 wherein the following additional step isincluded:

5. interlocking the core which is being cut with structure associatedwith the core barrel to thereby enable the core barrel to remainstationary with respect to the formation and to rotate with respect tothe drill pipe.

12. The method of claim 11 and including the following additional steps:

5. continuously flowing compressed fluid into the drill string annulusbefore and after step (40) is carried out; and

6. injecting liquid into the compressed fluid flow as the cores travelup the central passageway.

2. accumulating the cut cores in a core barrel;
 2. accumulating the cutcores in a core barrel;
 2. accumulating the cut cores in a core barrel;2. A method of drilling boreholes and obtaining cores therefrom, whereina drill bit is connected to concentrically arranged drill pipe whichforms a central and annular passageway for circulating fluid to and fromthe bit, comprising the steps of:
 2. breaking the core into convenientlengths which will facilitate their removal from the borehole; 2.Controlling the rate of penetration of the bit by maintaining a constantpressure drop across the face of the bit to thereby prolong the life ofthe bit;
 3. circulating drilling fluid down through the drill stringannulus, across the cutting face of the drill bit, and back up throughthe borehole annulus, while the bit cuts cores to form the borehole; 3.accumulating several lengths of cut core in a core barrel;
 3. The methodof claim 2 wherein the following additional step is included: 3.arranging the core barrel in journaled relationship with respect to thedrill pipe and stationary with respect to the formation by interlockingthe core which is being cut with structure associated with the corebarrel;
 3. restricting the flow of fluid from the central passageway ofthe drill pipe while carrying out step (2);
 3. retrieving the cores ofstep (2) by the following additional steps: a. restricting the flow offluid from the borehole and from the central passageway of the drillstring while increasing the pressure at the drill string annulus tothereby cause a rise in pressure at the drill bit; b. maintaining thebit in cutting relationship to the formation; c. removing the flowrestriction from the central passageway and circulating a major portionof the fluid from the drill string annulus, into the core barrel, andback up the central passageway to thereby provide a pressure drop acrossthe cores of step (2) in order to force the cores up through the centralpassageway of the drill string.
 4. interlocking the core which is beingcut with structure associated with the core barrel to thereby enable thecore barrel to remain stationary with respect to the formation and torotate with respect to the drill pipe.
 4. retrieving the cores of step(2) by increasing the flow of drilling fluid while maintaining the bitin cutting relationship to the formation and circulating a major portionof the fluid from the drill string annulus into the core barrel and backup the central passageway to thereby provide an increased pressure dropacross the cores in the core barrel which causes the accumulated coresto move from the core barrel to the surface of the earth.
 4. retrievingthe cores of step (2) by carrying out the following steps: a.restricting the flow of fluid from the borehole annulus by using theaction of the drill bit against the formation as a valve means; b.supplying a source of compressible fluid pressure to the annulus of thedrill string; c. increasing the flow pressure of the drilling fluidwhile maintaining the bit in cutting relationship to the formation; d.releasing the flow restriction from the central passageway to therebypermit a major portion of the fluid to flow from the drill stringannulus, into the core barrel, and back up the central passageway so asto move the accumulated cores from the core barrel to the surface of theearth.
 4. The method of claim 2 wherein step (4) includes the followingadditional steps: a. restricting the flow of fluid from the boreholeannulus by using the action of the drill bit against the formation as avalve means; b. supplying a source of compressible fluid pressure to theannulus of the drill string; c. releasing the flow restriction from thecentral passageway to thereby permit the flow of liquid, cores, andcompressed fluid therethrough.
 4. retrieving the cores of step (3) byincreasing the flow of drilling fluid while maintaining the bit incutting relationship to the formation to thereby provide an increasedpressure drop across the cores in the core barrel;
 4. accumulating thecut cores in a core barrel;
 5. retrieving the cores of step (4) byincreasing the flow of drilling fluid while maintaining the bit incutting relationship to the formation to thereby provide an increasedpressure drop across the cores in the core barrel; and, circulating amajor portion of the fluid from the drill string annulus, into the corebarrel, and back up the central passageway to thereby cause theaccumulated cores to move from the core barrel to the surface of theearth.
 5. circulating a major portion of the fluid from the drill stringannulus, into the core barrel, and back up the central passageway whenit is desired to retrieve the accumulated cores from the core barrel tothe surface of the earth.
 5. A method of drilling boreholes andobtaining cores therefrom, wherein the drill bit is connected toconcentrically arranged drill pipe which forms a central and annularpassageway for circulating fluid to and from the bit, comprising thesteps of:
 5. interlocking the core which is being cut with structureassociated with the core barrel to thereby enable the core barrel toremain stationary with respect to the formation and to rotate withrespect to the drill pipe.
 5. continuously flowing compressed fluid intothe drill string annulus before and after step (4c) is carried out; and6. injecting liquid into the compressed fluid flow as the cores travelup the central passageway.
 6. interlocking the core which is being cutwith structure associated with the core barrel to thereby enable thecore barrel to remain stationary with respect to the formation and torotate with respect to the drill pipe.
 6. The method of claim 5 whereinthe following additional step is included:
 6. interlocking the corewhich is being cut with structure associated with the core barrel tothereby enable the core barrel to remain stationary with respect to theformation and to rotate with respect to the drill pipe.
 7. The method ofclaim 5 wherein step (5) includes the following additional steps: a.restricting the flow of fluid from the borehole annulus by using theaction of the drill bit against the formation as a valve means; b.supplying a source of compressible fluid pressure to the annulus of thedrill string; c. releasing the flow restriction from the centralpassageway to thereby permit the flow of liquid, cores, and compressedfluid therethrough.
 8. A method of drilling boreholes and obtainingcores therefrom, wherein a drill bit is connected to concentricallyarranged drill pipe which forms a central and annular passageway forcirculating fluid to and from the bit, comprising the steps of:
 9. Themethod of claim 8 wherein the following additional step is included: 10.A method of drilling boreholes and obtaining cores therefrom, whereinthe drill bit is connected to concentrically arranged drill pipe whichforms a central and annular passageway for circulating fluid to and fromthe bit, comprising the steps of:
 11. The method of claim 10 wherein thefollowing additional step is included:
 12. The method of claim 11 andincluding the following additional steps: